a. Field of the Invention
Broadly speaking, this invention relates to frame location for a strip record medium retrieval system. More particularly, this invention relates to a frame location system for use with a microfilm retrieval system and is particularly useful in presenting a selected frame on a microfilm strip or reel to a predetermined station, such as a viewing station.
B. Discussion of the Prior Art
As known to those skilled in the microfilm retrieval art, a typical microfilm retrieval system includes apparatus for storing or housing a plurality of microfilm reels or strips and for presenting or delivering a selected microfilm reel or strip to a viewing station where the strip or film is unreeled and the documents are presented for viewing. Typically, each microfilm reel or strip has a plurality of frames thereon in which documents, or portions of documents, are recorded by the microfilming process. Each frame on each microfilm strip or reel is identified by what is generally referred to in the art as an "address," typically the numerical sequence or chronological order in which the frame appears on the microfilm. The frames and, hence, the documents recorded thereon are typically located by counting the frames.
In general, the frames are counted by means of frame or document indicia which are associated with the frames, and hence the documents, in a predetermined manner and which indicia are typically opaque to light whereby they may be sensed and counted by photodetectors. These frame or document position marks are typically referred to by those skilled in the art as "blips." Thus, for example, a microfilm strip having 10,000 frames thereon would have the frames numbered beginning with 0000 and ending with 9999 and frame address 6000 would be the address of the six-thousandth frame (and hence any document recorded thereon) appearing chronologically on the microfilm strip or reel. Accordingly, documents are typically retrieved and presented to a viewing station by selecting the numerical address of the frame in which the document is recorded on the microfilm strip or reel.
Numerous frame location systems for microfilm retrieval systems are known to the prior art; however, such prior art frame location systems are exceedingly complex and expensive and generally include inherent operating limitations which render them highly specialized for a particular purpose and thereby unsuitable for general commercial use. For example, the electronic, high-speed, strip record accessing control circuitry disclosed in U.S. Pat. No. 3,435,310 to E. F. Bradley, has the operating limitation that the strip record medium must have indicia or documents recorded thereon at predetermined intervals proportional to the increments to be accessed.